1. Field of the Invention
The present invention relates to a method, apparatus and computer program product providing a mechanism for controlling a connection of different types of subscribers to a communication network via different links to a core network. In particular, the present invention is related to a mechanism providing functions of a so-called hybrid home node B (HHNB) where subscribers, depending on their belonging to a specific subscriber group, such as a closed subscriber group or an open subscriber group, are admitted for a connection to the communication network via different connection routes and systems.
2. Related Background Art
Prior art which is related to this technical field can e.g. be found by the technical specifications TS 25.467 (current version: 9.1.0) of the 3GPP.
The following meanings for the abbreviations used in this specification apply:
3GPP—3rd generation partnership project
CSG—closed subscriber group
DeNB—donor eNB
DSL—digital subscriber line
eNB—enhanced node B (Base station)
GAN—generic access network
HHNB—hybrid HNB
HNB—home node B
HNB GW—home node B gateway
IP—Internet protocol
LTE—long term evolution
OSG—open subscriber group
RN—relay node
QoS—quality of service
UE—user equipment
UMA—unlicensed mobile access
WLAN—wireless local area network
In the last years, an increasing extension of communication networks, e.g. of wire based communication networks, such as the Integrated Services Digital Network (ISDN), DSL, or wireless communication networks, such as the cdma2000 (code division multiple access) system, cellular 3rd generation (3G) communication networks like the Universal Mobile Telecommunications System (UMTS), cellular 2nd generation (2G) communication networks like the Global System for Mobile communications (GSM), the General Packet Radio System (GPRS), the Enhanced Data Rates for Global Evolutions (EDGE), or other wireless communication system, such as the Wireless Local Area Network (WLAN) or Worldwide Interoperability for Microwave Access (WiMAX), took place all over the world. Various organizations, such as the 3rd Generation Partnership Project (3GPP), Telecoms & Internet converged Services & Protocols for Advanced Networks (TISPAN), the Internation Telecommunication Union (ITU), 3rd Generation Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), the IEEE (Institute of Electrical and Electronics Engineers), the WiMAX Forum and the like are working on standards for telecommunication network and access environments.
Generally, for properly establishing and handling a communication connection between network elements such as a UE and another communication equipment, such as a database, a server, etc., one or more intermediate network elements, such as network control elements, support nodes, service nodes and interworking elements are involved which may belong to different communication networks.
One approach to further develop telecommunication networks is the installation of so-called low-power base stations, which are also commonly referred to as “femto-cells” or home node B (HNB). Such low-power base stations are advantageous in that they are low-cost and possibly user-deployed cellular base stations using, for example, an IP based wired backhaul, such as cable or DSL, designed to provide service in local environments similar to existing WiFi access points.
Dense deployment of such low-power base stations offers significantly higher capacity per area as compared to macro cells, arising from using smaller cell sizes and more efficient spatial reuse. Femto-cells can be used to provide deep in-building broadband wireless services far more economically than a macro cellular network. Additionally, there can also be considerable savings associated with off-loading traffic onto the femto-cell, in particular for heavy data users.
According to current considerations, as done for example by 3GPP, corresponding low-power base stations (referred to hereinafter as HNBs) may appear like a normal (macro cell) base stations (for example like an eNB) for UEs so that there are no changes necessary in the UEs. The HNBs may provide access to a core network of a network operator, for example, via the Internet. For providing interfaces to the core network via the internet, different access systems can be provided, for example a so-called GAN, also known as UMA, which is chosen by 3GPP as the way to provide the interfacing to the operator's core network.
However, despite the benefits achievable by installing such low-power base stations or HNBs, there may arise also problems which have to be considered for guaranteeing proper functioning of telecommunication networks. For example, issues regarding interference management and efficient system operation are to be considered.
In general, roll-out of femto-cells can be seen as an introduction of an entirely new and unplanned network infrastructure using low-power base stations on top of a carefully planned and coordinated cellular network. For example, in the existing cellular networks, the used base stations are placed in specific locations that minimize the interference among the base stations. Therefore, for ensuring a minimal interference, femto-cells should use a dedicated part of the frequency spectrum so as to completely avoid interference problems, especially at the edges of macro-cells. However, such a solution may not be suitable in practice for several reasons, for example due to the unavailability of extra spectrum or the impossibility to clear-off channels for this purpose. Hence it is likely that femto- and macro-cells will share the same frequency band. In this case, possible capacity and coverage gains can dwindle away, for example due to macro/femto-cell co-channel interference.
Furthermore, other issues have to be considered further. For example, also in view of the fact that low-power base stations may be user-deployed cellular base stations, different aspects with regard to open subscriber groups (OSG) and closed subscriber groups (CSG) have to be considered. While a free-for-all OSG access mode of operation would be more appropriate from a spectrum efficiency point of view, the CSG access mode may be preferable with regard to security, privacy and fair resource distribution of the wired (x-DSL/cable) Internet connection aspects. CSG access mode ensures that only a relatively low number of “known” subscribers (or UEs) belonging for example to company members, friends or family members, can be served by the HNB. Also in view of possible legal consequences, a user running a low-power base station might not wish to share his/her Internet connection with other people, such as neighbors or persons being in the vicinity (and thus the coverage area of the HNB) simply to offload the macro-cell network. Therefore, an access restriction is to be expected.
On the other hand, if such other users are totally unable to access the cellular network via the nearby femto-cell whose signal may be much stronger than that of the (possible) far away macro-cell base station, interference will be a problem.
Furthermore, in case the HNB is linked to the core network by means of wired connections, such as DSL, a further problem may arise due to the capacity of the DSL line which may be lower than that of the link between the UE and the HNB, for example in case of a LTE air interface. Thus, the link between the HNB and the core network may become the bottleneck of such a system. As a result, even if the LTE air interface is not overloaded, congestion might occur on the DSL line affecting all users of the HNB, but also users connected directly to the DSL modem e.g. via Ethernet.